1. Field of the Invention
The present invention relates to cable terminals for end-face connection of the conductors of a multicore cable, the cable terminal having a plug part and a cable receiver that can be connected to one another, especially screwed to one another. In particular, the present invention relates to such cable terminals where the plug part is provided with contact elements and a core holding and guiding part with guidance channels where in the assembled state, the core holding and guiding part is located between the plug part and the cable receiver.
2. Description of Related Art
Initially, it will be explained below the meaning of the terms used herein below both with respect to the prior art and the present invention as well.                a) The term “cable” means an electrical line which has at least one core, but generally several cores. If there are several cores, it is a multicore cable. For cables with only one core, it is a single-core cable.        b) The cores of a cable includes a conductor and core insulation.        c) In one cable, the conductors are provided with core insulation which insulate the conductors. If there are several cores, the several cores, in their totality, are surrounded by other insulation such as the cable insulation. For a single-core cable, there is no other insulation besides the core insulation.        
It was stated above, the invention relates to a cable terminal or joining device for end-face connection of the conductors of a multicore cable. Here, the cable can be connected to an electrical device or can be joined in an electrically conductive manner to a second cable. If the cable is connected to an electrical device, it is a cable terminal. If two cables are to be connected to one another, it is a joining device. Regardless of whether it is a terminal or a joining device, the cable or conductor is always connected by a contact element and thus, the joining device which joins two cables is also considered herein as a terminal. As such, the embodiment of the present invention is shown where the terminal connects a cable to an electrical device. However, the terminal as used herein is can be used to connect two cables as well and hence, the term terminal also refers to the joining device in the present application.
In a terminal for electrically conductive connection of a cable to an electrical device, the electrical device should be understood generally. In particular, the expression “electrical device” also includes electrical and electronic components, means and devices.
It was stated initially that the cable terminal is intended for end-face connection of the conductors of a multicore cable. First of all, it is conventional in practice for multicore cables to be connected. However, the cable terminal can also be used for those cables which have only one core.
With the initially described cable terminal, cables are generally connected in which the cable insulation, but not the core insulation of the individual cores, has been removed before connection. The cable terminal thus enables connection of unstripped conductors. Possibilities for connecting unstripped conductors are already known from the prior art. For this purpose, so-called insulation piercing connecting devices or insulation displacement terminal devices are used in which the contact elements, which are generally made as contact blades, cut into the core insulation laterally from outside until contact is made with the conductor. In addition, there is a second possibility for connecting unstripped conductors in which the contact elements which are generally made as contact spikes do not pierce the core insulation, but penetrate into the conductor and/or the core insulation from the end face of the cores roughly in the direction of the lengthwise axis of the cores, and make contact with the conductor.
In the cable terminal to be formed with the present invention, the second possibility is used, i.e. the core insulation is not cut from the side, but the conductors are connected from the end face. In doing so, in this connection, stranded conductors are generally used. Thus, the contact element penetrates between the individual strands of the conductor. As a result of the restoration force of the core insulation, there is a clamping force sufficient for making electrical contact between the individual strands of the conductor and the contact element which has penetrated into the conductor.
German patent 44 18 259 discloses a cable terminal of the type under consideration in which the core holding and guiding part consists of a plug-side gland and a cable-side end part. In the installed state of the cable terminal, the gland is pushed into a corresponding recess in the plug part. The alignment of the individual conductors to the contact elements takes place by there being four axially parallel channels for holding the cores in the core holding and guiding part and they are flush with the contact elements in the installed state. Here, the inside diameter of the channels is slightly less than the outside diameter of the cores, by which on the one hand, clamping of the cores takes place, and on the other, via the corresponding alignment of the gland to the contact elements, the cores are also aligned to the contact elements. In addition, the cable-side end part of the core holding and guiding part is made elastic by the lengthwise slots located in the end part, by which clamping of the individual cores can be achieved for forces acting accordingly radially on the end part.
In the above described known cable terminal, exact alignment of the individual cores to the contact elements is dependent on the production tolerances of the gland of the core holding and guiding part to the corresponding recess of the plug part. In addition, for different cables with different diameters of the cores, different core holding and guiding parts are necessary. If a cable which is used has cores with smaller diameters than the core guidance channels, the alignment of the cores to the contact elements is inadequate.
German utility model 298 17 679 likewise discloses a cable terminal of the type under consideration, but which enables connection of different cables with different core cross sections. To do this, the core holding and guiding part consists of a rubber elastic material with axially parallel channels located in it. By squeezing the rubber elastic material together in the radial direction, the channel cross section is matched to the actual cross section of the inserted cores. But here, the disadvantage is that by squeezing together the rubber elastic material of the core holding and guiding part, not only is the channel cross section changed, but also the alignment of the channel middle to the contact elements are changed. Thus, insertion of cores with different diameters into the core guidance channels of the core holding and guiding part is indeed possible, but the accuracy of alignment of the inserted cores to the contact elements likewise, depends on the core cross sections used so that exact alignment cannot always be ensured. In addition, the alignment of the cores is adversely affected by aging and settling phenomena of the rubber elastic core holding and guiding part.